Temperature sensors are utilized in a wide variety of applications in which it is necessary to monitor the temperature within a space. For example, cold rooms are used for storage of perishable goods in which the goods much be kept within a specified temperature range to prevent spoiling of the goods. Temperature sensors are commonly utilized in such areas to monitor the temperature within the area to ensure that the temperature does not increase to a point where the goods may be at a risk of spoilage. In such applications, a separate temperature sensor is connected to an alarm system to provide for a warning if the temperature increases beyond a particular limit. This limit is generally set at the factory when the unit is manufactured and provides for a temperature sensor set point for the temperature sensor. If the temperature detected by the temperature sensor exceeds the temperature set point established during the manufacture of the unit, then the alarm system indicates the alarm. In applications where it is necessary to monitor more than one set point, such as an upper and a lower limit, a second separate temperature sensor is commonly utilized with its own individual set point distinct from the set point of the first sensor. These sensor set points are generally established during the manufacture of the unit and are not field programmable.
In addition to cold rooms, there are many other applications which utilize temperature sensors. For example, storage areas where products are stored which must be kept from freezing are required to have the temperature monitored to ensure that it does not fall below a level at which the products may freeze. Another example would be greenhouses utilized for production for commercial crops, particularly high value crops such as exotic plants and flowers as well as certain herbs. It is critical in such applications to maintain the temperature in the greenhouse within an acceptable growing range, while also ensuring that the temperature has not reached a level which would cause permanent damage to the crops, either by the temperature dropping below a level where the crops would be damaged, or increasing to a level where the crops would be damaged.
At the present time, in such circumstances, it is necessary when one wishes to monitor a variety of temperature set points, that separate temperature sensors are required for each of the set points to be monitored. In addition, once the temperature set points are established in the unit, it is extremely difficult for these temperature set points to be modified or changed, often requiring the unit to be returned to the factory for changing of the temperature set points.
Alarm systems which include a temperature sensor function require the temperature sensor to be an individual device, separate and apart from other devices of the alarm system. The provision of the temperature sensor as a separate device increases the cost of the alarm system installation both in terms of cost of the devices as well as in cost of the installation of the alarm system, as the temperature sensor requires its own wiring and interface to the alarm control panel. If the temperature sensor function could be provided as part of another alarm system device, the complexity and cost of the alarm system could be reduced.
There therefore remains a need for a means of providing a device for an alarm system with a temperature sensor function, where the set point of the temperature sensor is easily programmable. There also remains a need for an alarm system which would allow for monitoring of multiple temperature set points and in which the set points can be easily programmed depending upon the situation or location at which the alarm system is located.